The present invention relates to a method of cleaning metal products and components, for example, aluminum precision parts such as head and photosensitive drum of video tape recorder (VTR), mainly for the purpose of degreasing, and a cleaning apparatus used in such method.
Hitherto, aluminum precision parts such as VTR head and photosensitive drum were cleaned by immersion ultrasonic cleaning or vapor cleaning by using chlorofluorocarbons or trichloroethane as cleaning fluid. However, chlorofluorocarbons and trichloroethane are ozone layer destroying substances, and their use is regulated, and they are being replaced by organic solvents such as methylene chloride and methanol (see the Japanese Laid-open Patent No. 3-144459). Besides, a degreasing cleaning apparatus using a water-based detergent such as alkali or surface active agent has been also developed.
Chlorofluorocarbons and trichloroethane are thus restricted, and methylene chloride and other organic solvents are harmful for human health and also involve problems in safety of work such as explosiveness.
Water-based detergents have side effects such as discoloration of the work surface, and it is extremely difficult to remove detergents by rinsing. The water-based detergent can easily remove oil chemically (wettable in water) and clean, but it means difficulty in separation into oil and water after cleaning. Therefore, in cleaning by using such water-based detergent, waste water treatment is huge in scale, requiring a wide area of installation and a high facility cost.
In the light of the above background, it is hence a primary object of the invention to present a cleaning method free from side effects such as discoloration of work surface, by using only purified water which is harmless to human health and environments as cleaning fluid, while obtaining the same cleanliness as in the conventional cleaning with chlorofluorocarbons or trichloroethane, and a cleaning apparatus used in such method.